1. Field of the Invention
The present invention relates to a transmission casing for an automotive vehicle and, more particularly to a transmission casing which comprises a front casing and a rear casing.
2. Description of Related Art
Typically a transmission casing for containing a transmission mechanism therein comprises a front part casing and a rear part casing which are connected. As shown in FIG. 12, a transmission casing "a" for containing a transmission mechanism "b" and a clutch "c" therein is divided into two parts, namely, a front part casing "a.sub.1 " and a rear part casing "a.sub.2." The transmission mechanism "b" includes an input shaft "d," a main shaft "e" and a counter shaft "f" on which a plurality of gears and a synchro-mesh mechanism are mounted so as to provide a plurality of gear ratios. The transmission mechanism further includes a control rod "g" for actuating the synchro-mesh mechanism as well as a shift mechanism. The shaft mechanism cooperates with a detent mechanism and a mis-shift prevention mechanism. A large portion of these elements is arranged within the transmission casing "a." The clutch "c" has a relatively large diameter and is placed within a front portion of the front part casing "a.sub.1." In order to receive compactly the clutch "c", which has a large diameter, the front part casing "a.sub.1 " as a front portion, shaped as a frustum of a, steeply inclining cone steeply inclining, and a cylindrically shaped rear portion.
If such a transmission casing has low structural stiffness, the transmission casing tends to generate noise due to vibration transmitted thereto. Consequently, the transmission casing must have a high structural stiffness. From the standpoint of structural stiffness, the transmission casing "a," which has a cylindrical shape from a middle portion to the rear part casing, is not always advantageous. Because the transmission includes a number of mechanical elements therein, the transmission casing is generally bulky and, accordingly, must be improved so as to be compact in size or geometry.